Bearings are devices that permit constrained relative motion between two parts. They may be used in many different types of machinery to retain and support rotating components such as, for example, a wheel on a vehicle, a vane on a windmill or a drum in a washing machine. A typical bearing comprises inner and outer rings and a plurality of rolling elements, and may further comprise a cage to retain the rolling elements.
During use, the bearing is subjected to different loads, both static and dynamic. The static load is mainly due to the weight supported by the bearing and may also be due to a preload with which the bearing is mounted. The dynamic loads are time-dependent and are due to the operating conditions.
In many systems, it is desirable to be able to monitor the load acting on a bearing. In modern vehicles, for example, load data from the wheel bearings are used in the control of vehicle stability systems. Vibration is another physical parameter that is important with regard to bearings, as it provides an indication of the ‘health’ of a bearing. Excessive vibration may be a sign that a bearing is nearing the end of its life, and so bearings in vital machinery are often provided with sensors to monitor vibration.
Displacement sensors such as strain gauges are commonly applied to measure load and deformation, while thin film piezoelectric transducers may be used as vibration sensors. Preloaded piezoelectric sensors can also be used as displacement sensors, which involves clamping the sensor to e.g. a bearing ring.
A widely applied method of attaching a sensor to a bearing component is adhesive bonding. This method has a number of drawbacks. The surface of the bearing component needs to be cleaned and pretreated, and the adhesive may need to cure for several hours before it has stabilized.
The present invention aims to address at least some of the problems associated with the prior art and to provide an improved combination of a bearing component and a sensor.